Preheat oven to 375. Melt butter. Combine cake mix and oats in a largebowl; stir in the melted butter until the mixture is crumbly. Measure half of this mixture(about 3 cups) into a greased 13 x9x3 inch pan. Press firmly into pan to cover the bottom. Combine preserves and water; spoon over crumb mixture in pan, and spread evenly. Cover with remaining crumb mixture. Pat firmly to make top even. Bake at 375 for 20 minutes--top should be very light brown. Cool completely before cutting into bars.